Ruby Walsh was last night dramatically ruled out of his fourth Grand National since 2010 after suffering a hairline fracture to his wrist when Blood Cotil fell in the Topham Chase at Aintree.

Willie Mullins confirmed that Nina Carberry will partner Walsh's intended National mount Sir Des Champs, which had been backed from 40/1 into 16/1 after Walsh's decision to ride him.

Paul Townend steps in on odds-on shots Douvan and Yorkhill. It is a cruel blow for 36-year-old Walsh, who also had a crashing fall off hot favourite Vautour prior to the Topham. In 2010 and 2012, he suffered similar fates, when sidelined after Aintree Hurdle spills from Celestial Halo and Zarkandar, while he also missed the 2014 National due to injury.

The injury may also cost the 10-time champion his Irish title, as he is just 10 clear of Bryan Cooper.

His misfortune left a sour note on the day. Mullins' first 14 runners on the card failed to score, including favourites Limini and Bellshill, which was just touched off under Patrick Mullins, who was standing in for Walsh.

Then the champion amateur led home stablemate Battleford on Bacardys in the bumper. With £1m up for grabs in the Crabbie's Grand National, Willie Mullins leads Paul Nicholls for a first time by nearly £55,000 in the British trainers' championship.

With four runners among a total of 13 Irish contenders in today's National, his assault on the cross-channel title is gathering momentum.

It may not be decided at Aintree or Sandown, either. Hazel Peplinski of Perth racecourse, where a three-day Festival begins on Wednesday week, tweeted that Mullins had "mentioned he has scanned @PerthRacecourse programme and pencilled in a squad of 12!!" No stone, it seems, will be left unturned.